Oat cell carcinoma of the lung is a rapidly fatal disease requiring aggressive initial combination chemotherapy. Sequential studies at the BCRP utilize combinations of active agents (cyclophosphamide, doxorubicin, and VP 16-213 as the basic regimen; and CCNU, methotrexate, vincristine, and procarbazine as an alternating regimen). One-hundred-and-thirty evaluable patients have been entered onto the sequential studies utilizing basic combination or alternating chemotherapy. Immunotherapy was not found useful for response or survival. The overall response rate now in two sequential studies continues to be over 90% with 60% complete remission rate in limited disease. Median duration of survival was 9-1/2 months and 16 months for patients with extensive and limited disease respectively. Among patients with limited disease, there is a projected 20 to 30% longterm disease free survival. Alternating chemotherapy has not provided improvement in response rate or survival. These sequential studies demonstrate that chemotherapy alone is an effective treatment modality. Toxicity in these studies was manageable by dose modification.